This invention relates to a manufacturing method for a sensor, and more particularly to a method of manufacturing a sensor in which an electrode interval of a capacitance element is changed or a mechanical deformation is induced in the piezo resistance element on the basis of force applied to a weight body by action of acceleration or angular velocity, thus making it possible to detect direction and magnitude of acceleration or angular velocity applied thereto as a change of an electrostatic capacitance or a resistance value.
In the automobile industry or the machinery industry, etc., there has been increased demand of sensors capable of precisely detecting physical action such as force, acceleration, angular velocity or magnetism. Particularly, compact sensors capable of detecting these physical actions every two-dimensional or three-dimensional components have been expected. In order to meet such demand, there are disclosed, in U.S. Pat. No. 5,492,020, U.S. Pat. No. 5,497,668, U.S. Pat. No. 5,421,213 and U.S. Pat. No. 5,406,848, a fundamental structure of the sensor capable of detecting force, acceleration or magnetism by utilizing a change of an electrostatic capacitance. Moreover, in U.S. Pat. No. 5,646,346, a sensor capable of detecting angular velocity by utilizing a change of an electrostatic capacitance is disclosed. These sensors have a function to detect, as a change of an electrostatic capacitance value, force directly applied from the external or force applied resulting from acceleration, magnetism or angular velocity. Namely, since an electrode interval of a capacitance element is changed on the basis of force applied to a weight body, the applied force can be detected as a change of the electrode interval by measuring a change of an electrostatic capacitance value of the capacitance element.
Further, in U.S. Pat. No. 4,905,523, U.S. Pat. No. 4,969,366, U.S. Pat. No. 4,967,605, U.S. Pat. No. 5,182,515, U.S. Pat. No. 5,092,645, and U.S. Pat. No. 5,263,375, etc., sensors for detecting force/acceleration/magnetism by utilizing a piezo resistance element are disclosed. In these sensors, there is employed a structure in which mechanical deformation takes place in the piezo resistance element on the basis of force applied to a weight body, and detection is carried out on the basis of a change of a resistance value of the piezo resistance element.
In order to popularize utilization of such sensors in various industrial fields, reduction in cost by mass-production is indispensable. In view of the above, e.g., in U.S. Pat. No. 5,531,002, there is disclosed a manufacturing method suitable for mass-producing three-dimensional acceleration sensors utilizing change of electrostatic capacitance. In U.S. Pat. No. 5,014,415, there is disclosed a manufacturing method suitable for mass-producing a three-dimensional acceleration sensor utilizing piezo resistance elements. These manufacturing methods utilize semiconductor processing which is widely used for manufacturing semiconductor integrated circuits. In accordance with this method, necessary processing is implemented onto a substrate surface of silicon etc., and plural substrates are stacked to constitute a substrate body having multi-layers. Then the substrate body is cut to manufacture a large number of sensors at the same time. According to this manufacturing method, a large number of sensors can be produced at low cost similarly to the manufacturing process of the typical semiconductor integrated circuit.
In accordance with the above-described manufacturing method, considerably compact sensors can be provided. In the industrial field, never the less, further miniaturization of sensor is expected. However, with the above-described conventional manufacturing method, further miniaturization on the commercial base is very difficult. Namely, in order to detect force applied to the weight body as a change of distance between electrodes which constitutes a capacitance element or to detect it as a change of resistance value of a piezo resistance element, it is necessary to produce a sensor structural body having specific physical structure. However, with the conventional typical semiconductor manufacturing process, it is very difficult to produce a fine sensor structural body.
For example, in order to quarry a weight body from a single semiconductor substrate, it is necessary to dig grooves on the substrate. Especially, a thin and deep groove should be made on the substrate for realizing miniaturization. However, it is difficult to make a thin and deep groove by using an etching method generally utilized in the semiconductor manufacturing process. On the other hand, when a mechanical cutting method using a dicing blade is applied, it is possible to make a thin and deep groove on the substrate. However, this mechanical cutting method has another problem of cracking. The more the sensor structural body becomes compact, the more cracking is apt to take place on the semiconductor substrate when the mechanical processing is applied. As a result, mass-production on the commercial base becomes difficult in point of yield.
In view of the above, an object of this invention is to provide a method of manufacturing a sensor utilizing an electrostatic capacitance element or a sensor utilizing a piezo resistance element, in which mass-production of more compact sensors can be realized on the commercial base.